Grading & Level of Importance: B
3 % of women of reproductive age in US infected, estimated rate of asymptomatic cases = 50 %. 180 million new infections worldwide annually, according to WHO.
A sexually transmitted infection caused by the protozoan parasite Trichomonas vaginalis.
Aetiology & Pathogenesis
The causative agent T. vaginalis is a flagellated protozoan parasite transmitted during sexual intercourse. Transmission usually occurs via direct, skin or mucosal contact with an infected individual, most often through vaginal intercourse. Females can acquire the disease from infected males or females, but males usually acquire it only from infected females.
Signs & Symptoms
The incubation time is usually 1-2 weeks, but up to half of infected females have no symptoms and can be asymptomatic carriers for years. Most symptomatic females have vaginal discharge with an offensive odour. The classic symptom is a yellow-green, frothy discharge, which is present in less than 10 % of symptomatic females. Other symptoms include pruritus vulvae and vaginal burning sensation. There can also be dysuria and pain or bleeding during sexual intercourse. The cervix may have a punctate or strawberry-like appearance.
T. vaginalis is present in 30-70 % of the male partners of infected females, but most infected males have no symptoms. If there are symptoms, they are usually a result of urethritis (urethral discharge, meatal irritation, and dysuria).
No classification applicable.
Laboratory & other workups
In women, a vaginal or cervical smear with direct microscopy. In men a urethral swab (women:a high vaginal or cervical swab) for culture. Nucleic acid amplification test and tests detecting Trichomonas antigens in urethral or cervical smears are also available.
The infection may cause acute symptoms, but the majority of patients have no symptoms and can be asymptomatic carriers for years.
Based on typical clinical features and microbiological confirmation. Mixed STI infections to be excluded.
Vulvovaginitis due to other causes (candida, bacterial vaginosis, aerobic vaginitis); chlamydial urethritis, gonorrhoea and mycoplasma urethritis. Genital herpes simplex can also cause similar symptoms.
Prevention & Therapy
Transmission can be prevented by barrier contraception.
First-line treatment consists of metronidazole p.o. 400–500 mg × 2-3 for 5-7 days or as a single dose of 2 g and is usually effective. The alternative is tinidazole as a 2 g single dose p.o. It is important also to treat the sexual partner of the patient. Sexual activity should not take place until symptoms have cleared.
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